Let's now consider the principles that should be followed when formulating a mechanism. This is rather philosophical or ethical question and was studied by numerous great scientists and humanists including Jeremy Bentham, John Stuart Mill, John Locke, John Rawls and John Forbes Nash. The paramount idea looming above all notions and theories, apart from the malevolent, is "\textit{equal treatment of equals}" i.e. behaviour toward two agents can vary only if they are of different profiles. This concept may be trivial, however it is crucial when assessing a mechanism.

\textit{Equal treatment} consist of four basic rules:
\begin{itemize}
\item \textit{Exogenous rights}

The best example for Exogenous rights is an ordinary voting rule giving the same power to each voter regardless of his political preferences, gender, wealth or creed. %------heritage? other example

\item \textit{Compensation}

It means sharing more goods to the agents who need them most, e.g. after natural disaster, support from charity should be distributed at first to those who were deprived of most of their properties.

\item \textit{Reward} 

Agent's share is proportional to her contribution or influence. Analogically, when sharing "bads" instead of goods, agent's cost is proportional to her impact or fault.
 
\item \textit{Fitness} 

This is the most vague criterion which can easily be misinterpreted. The main idea is that resources should be distributed to whomever makes the best use of them.
\end{itemize}


%\subsubsection{4 principles - flute example}
%\begin{itemize}
%\item 1st child - few toys - compensation
%\item 2nd child - heritage - exogenous rights
%\item 3rd child - cleaned and fixed flute - reward
%\item 4th child - musical talent - fittness
%\end{itemize} <- TODO to chyba wypieprzyc

%\begin{itemize}
%\item cardinal scale in preference relation
%\begin{itemize}
%\item relation - complete, transitive, over feasible set of choices
%\end{itemize}
%\end{itemize} <- TODO to w cardinal welfarism

%\begin{itemize}
%\item collective utility function
%
%\begin{itemize}
%\item benthams utilitarian imperative - orthogonal to the compensation principle (e.g. minority may be sacrificed)
%
%\item rawls' egalitarianism - embodiment of compensation
%
%\item nash' CUF - product of individual utilities; compromise between bentham and rawls
%\end{itemize}
%\end{itemize}
%
%\begin{itemize}
%\item public contract
%
%\begin{itemize}
%\item large community - hard to achieve compromise (without benevolent dictator)
%\item small community - e.g. divorce case - emotionally difficult to reach reasonable settlement
%
%\item share cropping
%\item profit sharing (artist-manager/writer-publisher)
%\item bancruptcy settlements
%
%\item public authority - benevolent dictator, who is treating agents utility profiles as multicriteria decision situation and trying to make decision that all parties can easily adopt
%\end{itemize}
%\end{itemize}
%
%
%\begin{itemize}
%\item compensation - equality ex post
%\item exogenous rights - equality ex ante
%
%\item fittness:
%\begin{itemize}
%\item sum-fittness - $max{\sum_i{u_i}}$ - aggregation function - utilitarianism
%\item efficiency-fittness - pareto-optimality - weaker condition
%\end{itemize}
%\end{itemize}
%
%% TODO
%IIA !!! <- to w criteria
